Coffee husk is an abundant agro-industrial byproduct rich in lignocellulosic fibers, making it a promising natural filler for sustainable polymer composites. Utilizing coffee husk helps reduce environmental impact by valorizing coffee processing waste and supports circular economy initiatives in material production.

The coffee husk, an abundant by-product, is transformed into rigid objects such as reusable cups and mugs primarily made from recycled polymers loaded with coffee husk. These objects are more resistant to chipping than ceramics and retain heat better than glass. They are durable, reusable, and can eventually be recycled into new products. However, the recyclability or compostability of these products depends on the amount and type of husk used and on food-contact regulations varying by country.

Coffee husks are also used as recycled material for producing lightweight composite blocks or panels suitable for affordable housing construction, especially in remote or low-income areas. Their chemical composition makes them suitable as lightweight aggregates in concrete, offering good thermal insulation properties. However, the high carbohydrate content slows cement setting, an issue overcome by mineralizing the coffee husks.

Studies have shown its successful incorporation in various polymer matrices. For instance, polyethylene-based composites with 20–40 wt% coffee husk demonstrated good dispersion and fiber exfoliation during processing, which enhanced fiber-matrix contact. These composites exhibited increased stiffness and hardness due to improved crystallinity while maintaining adequate processability (Jaramillo et al., 2021).

Coffee husk has also been explored in biopolymers like PHBV, where its inclusion improved sustainability with favorable mechanical and thermal properties relative to other natural fillers (Janowski et al., 2024). Furthermore, coffee husk has found applications in biomedical PMMA composites (Fouly et al., 2023) and as a filler in cement pastes (Miranda et al., 2024), contributing to improved mechanical properties and hydration behavior. Additionally, coffee husk has been proposed as a sustainable filler in plywood production, demonstrating promising performance with lower environmental impacts compared to conventional materials (Wronka et al., 2025).

Source:

• Fouly, A., Alnaser, I. A., Assaifan, A. K., & Abdo, H. S. (2023). Developing PMMA/coffee husk green composites to meet the individual requirements of people with disabilities: Hip spacer case study. Journal of Functional Biomaterials, 14(4), 200. https://doi.org/10.3390/jfb14040200
• Jaramillo, L. Y., Vásquez-Rendón, M., Upegui, S., Posada, J. C., & Romero-Sáez, M. (2021). Polyethylene-coffee husk eco-composites for production of value-added consumer products. Sustainable Environment Research, 31, Article 34. https://doi.org/10.1186/s42834-021-00107-6
• Janowski, G., Frącz, W., Bąk, Ł., Sikora, J. W., Tomczyk, A., Mrówka-Nowotnik, G., & Mossety-Leszczak, B. (2025). Effect of coffee grounds content on properties of PHBV biocomposites compared to similar composites with other fillers. Polymers, 17(6), 764. https://doi.org/10.3390/polym17060764
• Miranda, E. H. N., Marcelino, T. O., Kuhn, L. S., Gomes, D. R., Vitorino, F. P., Mendes de Andrade, R. C., & Ferreira, S. R. (2024). The influence of coffee husk ash as a filler addition in mechanical and hydration properties of cement pastes. Journal of Engineering Research, 4(1). https://doi.org/10.22533/at.ed.1317412415016
• Wronka, A., Del Valle Raydan, N., Robles, E., & Kowaluk, G. (2025). Coffee silverskin as a sustainable alternative filler for plywood: Characterization and performance analysis. Materials, 18(7), 1525. https://doi.org/10.3390/ma18071525